1. Field of the Invention
The present invention relates to a belt fabric which is provided at a part of a power transmission belt on which frictional forces act, to a power transmission belt using such a belt fabric, and to a high load power transmission V-belt using such a belt fabric.
2. Description of the Prior Art
Synchronous belts are belts of the type in which belt teeth are provided at specified pitches in the belt longitudinal direction and transmit power by meshing of the belt teeth with their cooperating pulleys. During power transmission by such a synchronous belt, a great frictional force acts on the belt teeth. In general, in a typical synchronous belt made of rubber, its belt tooth side surface is covered with a belt fabric in order to inhibit abrasion of the belt and chipping of the belt teeth due to such abrasion. Prior to molding of the belt, the belt fabric is subjected to dipping into a rubber solution prepared by dissolving a non cross-linked rubber composition in an organic solvent, and subsequently to drying, in order that the belt fabric may be given cushioning properties, adhesive properties to the belt main body, and other properties. Meanwhile, with a view to improving the heat resistance of the belt main body of the synchronous belt, besides the hydrogenated nitrile rubber (hereinafter “H-NBR”) composition cross-linked by sulfur, other H-NBR compositions such as an organic peroxide cross-linked H-NBR composition, have been used as a rubber composition for belt main body formation. Further, with a view to enhancing the rigidity of the belt teeth thereby to improve the resistance to high load of the belt, H-NBR compositions of the organic peroxide cross-linking group reinforced by addition of zinc methacrylate have been used as a rubber composition for belt main body formation in recent years. With such improvement in the heat resistance of the belt main body, improvement also in the heat resistance of rubber ingredients deposited on the belt fabric as a result of dipping into a rubber solution has been required. To this end, a rubber solution of the type prepared by dissolving a non cross-linked H-NBR composition of the organic peroxide cross-linking group in an organic solvent may possibly be used.
Typical high load power transmission V-belts include an endless band having a tensile band main body formed of a rubber composition and a plurality of blocks each of which can be brought into engagement with the tensile band for fastening thereto so that the plurality of blocks are disposed side by side at intervals in the longitudinal direction of the tensile band, and power is transmitted by friction of the plurality of blocks against its cooperating pulleys. During such power transmission by the high load power transmission V-belt, friction forces will act on the upper and lower surfaces of the tensile band because of the back-and-forth rocking of the blocks. Therefore, such a high load power transmission V-belt is generally provided with a top fabric and a bottom fabric on the upper and lower surfaces of its tensile band, respectively, for inhibiting abrasion of the tensile band and block damage by block joltiness due to such abrasion of the tensile band. And, as in the aforesaid synchronous belt, the top and bottom fabrics are subjected to dipping into a rubber solution prepared by dissolving a non cross-linked rubber composition in an organic solvent, and subsequently to drying, prior to molding of a tensile band. Meanwhile, high load power transmission V-belts are usually used under extremely severe conditions (for example, sever temperature conditions). To cope with this, H-NBR compositions of the organic peroxide cross-linking group mixed with zinc methacrylate have been used as a rubber composition for forming a tensile band main body of the high load power transmission V-belt. And, with such enhancement in the performance of the tensile band main body, improvements in the heat resistance of rubber ingredients deposited on the top and bottom fabrics as a result of dipping into a rubber solution have been required. To this end, a rubber solution of the type prepared by dissolving a non cross-linked H-NBR composition of the organic peroxide cross-linking group in an organic solvent may possibly be used.